1. Field of the Invention
The present invention relates to a mounting structure for a cam-type torque damper for use in damping torque variation when power is transmitted from, for example, a crankshaft of an engine to a primary gear.
2. Description of the Background Art
An example of a cam-type torque damper of this kind is shown in FIG. 6. This device is spline connected with a collar 102 on an outer circumferential surface of an axial end portion of a crankshaft 101, and a primary gear 103 is rotatably fitted on the collar 102. A concave cam 104 is formed in a side of the primary gear 103, and a lifter 106 having a convex cam 105 formed at one end thereof for mesh engagement with the concave cam 104 is fitted on the collar 102 axially movably through spline connection. Furthermore, a spring 107 is provided for biasing the lifter 106 toward the primary gear 103, and the spring 107 is supported at one end thereof by a spring holder 108. This spring holder 108 is fixed with a nut 109 which is held in a distal end of the collar 102 and screwed to a distal end of the rotating crankshaft 101.
With the construction described above, when there occurs a torque variation in the crankshaft 101 and an excessive torque is transmitted, the lifter 106 is moved axially outwardly of the collar 102 against the spring 107 through the mesh engagement of the concave cam 104 with the convex cam 105, and the excessive torque is designed to be damped by virtue of a radial reaction force at the mesh engagement portion of the concave cam 104 with the convex cam 105.
In the case of the above construction, since the cam-type torque damper is assembled by assembling all the constituent components onto the axial end of the crankshaft 101 sequentially, they are required to be so assembled on the assembly line of vehicle bodies. This increases the assembling time on the assembly line, and therefore improvement of the assembling properties is desired. In addition, the performance of the cam-type torque damper with respect to mounting structure cannot be guaranteed on the assembly line. Also, since many labor hours are required to assemble and disassemble the cam-type torque damper, improvement of the maintenance properties is desired.
Furthermore, since the positioning means for positioning the spring holder 108 with respect to the thrust direction and the mounting means for mounting the cam-type torque damper itself on the rotating shaft become the same, and more specifically, since fastening by the nut 109 is used as such means, in the event that there occurs loosening at the fastened portion, this may cause a risk that the performance of the product varies, and therefore a structure free from loosening is desired.
It is therefore an object of the present invention to realize the aforesaid desires and solve the above problems by provided a mounting structure for a cam-type torque damper comprising a collar mounted on a rotating shaft for rotation together with the rotating shaft and a gear movably supported on the collar, a lifter having a cam formed thereon for abutment with a side of the gear and adapted to move axially over the collar, a spring for biasing the lifter toward the gear, and a spring holder for fixing one end of the spring, wherein torque variations generated on the rotating shaft are damped by virtue of a reaction force of the spring generated as the lifter moves. The mounting structure is characterized in that the gear, the lifter, the spring and the spring holder are assembled onto the collar in that order, and that the spring holder is positioned with respect to a thrust direction by a positioning member mounted on an outer circumference of the collar.
As this occurs, the positioning member may be a cotter pin or a circlip that is fitted in an annular groove formed in the outer circumference of the collar.
Since the thrust direction position of the spring holder is fixed to the collar with the positioning member, the cam-type torque damper can be pre-assembled together as an integral unit, and then attached to the crankshaft traveling on the assembly line. Then, the assembled cam-type torque damper can be mounted on the rotating shaft with a bolt or the like, and the damper is made integral with the rotating shaft. Consequently, since the pre-assembled cam-type torque damper can be attached as a small assembly on the assembly line of the vehicle bodies, the performance of the cam-type torque damper can be guaranteed, and moreover the assembling speed on the assembly line of vehicle bodies can be increased. In addition, since assembling and disassembling at the time of servicing becomes easy and quick, the maintenance properties are improved.
Since the thrust direction positioning means for the spring holder and the mounting means for mounting the spring holder on the rotating shaft are separated, the position of the spring holder with respect to the thrust direction can be made constant. In addition, since no loosening occurs in the thrust direction positioning means, the performance of the cam-type torque damper can be maintained over a long period of time.
When the load of the spring as the positioning means is relatively small, the circlip can be used, and the fixation can be attained simply with the circlip. In contrast, when the load of the spring is large, the cotter may be used to adjust the required strength freely by adjusting the thickness thereof.
Further scope of applicability of the present invention will become apparent from the detailed description given hereinafter. However, it should be understood that the detailed description and specific examples, while indicating preferred embodiments of the invention, are given by way of illustration only, since various changes and modifications within the spirit and scope of the invention will become apparent to those skilled in the art from this detailed description.